Reed relay



July 20, 1965 F. c. usuzzo ETAL 3,195,232

REED RELAY Fil ed Dec. 14, 1962 s Sheets-Sheet 1 INVENTORS F. C. LISUZZO AND C.E.COLWELL JR.

THEIR ATTORNEY July 20, 1965 REED RELAY Filed Dec. 14, 1962 3 Sheets-Sheet 2 FIG. 5D

5'8 I g In Y INVENTORS O L'- F.C. usuzzo AND LI By c. E.COLWELL JR.

THEIR ATTORNEY F. C.LISUZZO ETAL 3,196,232

July 20, 1965 F. c. LISUZZO ETAL 3,196,232

REED RELAY Filed Dec. 14, 1962 3 Sheets-Sheet 3 Qcu INVENTORS F. C. LISUZZO AND BY C. ECOLWELL JR.

THEIR ATTORNEY United States Patent 3,196,232 REED RELAY Frank C. fistula and Qharies E. Qolweil, In, Rochester,

N.Y., assignors to General Signal Corporation, Rochester, NFL, a corporation of New York Filed Dec. 14, 1%2, Ser. No. 244,647 15 Qlaims. (Cl. 2tttl87) This invention relates to electromagnetic relays, and more particularly, to sensitive relays of the reed switch type.

Reed relays generally comprise a reed switch and an actuating cci-l wound cylindrically around the switch. The reed switch generally comprises a reed of magnetic material supported as a cantilever near one end of the reed switch, and is constructed in the form of a flat strlp. A front contact and a back contact, each comprising fiat metallic strips, are mounted as cantilevers near the other end of the reed switch with their flat surfaces parallel to each other and to the fiat surface of the reed. The front and back contacts overlap the reed, enabling the reed to bear against either the front or back contact. The contact surfaces, which comprise the overlapping areas of the reed and both contacts, are usually thinly coated with a noble metal such as gold, in order to reduce corrosion and maintain high conductance at the contact surfaces. The reed switch is hermetically sealed within a non-magnetic electrically insulating material, usually glass. The hermetically sealed structure is usually tubular in form and may either be evacuated or contain therein an inert gas in order to protect the contacts from oxidation.

For proper operation, in reed switches of this type the back contact must be non-magnetic, and the reed and front contact must be magnetic. Both the contacts and the reed must obviously be electrical conductors. Moreover, while the reed is comprised of a resilient material, the front and back contacts must be comprised of a relatively non-resilient material.

When current flows through the actuating coil, an axially-directed magnetic field is created within the interior of the coil. This field induces opposite magnetic poles in the magnetic material just below the non-magnetic contact surfaces of the reed and front contact, thereby producing an attractive force between the reed and front contact at the contact surfaces. When this force is increased above a predetermined magnitude, it causes opening of the back contact and closing of the front contact. Upon deenergization of the actuating coil, the attractive force between the reed and front contact becomes substantially zero, so that the reed breaks the front contact and makes the back contact, under its own inherent resilience.

Relays of the type described operate with certain inherent disadvantages. For example, pick-up and dropout values of current for operating the relay can be dependent upon direction of current flow through the actuating coil and direction of current flow through the reed switch. In other words, incorporation of such relay into a circuit may be dependent upon polarity of connections in the circuit. Thus, with current flow through the coil in a given direction, certain pick-up and drop-out values of current are established. These values, however, are often different from pick-up and drop-out values when current flow through the actuating coil is reversed. Likewise, pick-up and drop-out values are often different from the established values when current flow through the reed switch is reversed. Moreover, this effect becomes more pronounced as amplitude of reed switch current is increased.

This phenomenon may be explained by consideration of magnetic flux paths in the relay created by flow of current through the coil and the reed switch. Because it is virtually impossible to align the reed switch precisely parallel with the magnetic field produced within the actuating coil, the reed switch can be positioned only in a general axial direction. As a result of this misalignment, coil flux may be considered to have a component acting longitudinally through the reed switch and a component acting perpendicular to the reed switch. The component acting longitudinally through the reed switch has the greatest effect on relay operation, since it induces the opposite magnetic poles at the contact surfaces of the reed switch. However, the component acting vertically upon the reed also has an effect on relay operation, as will be pointed out, infra.

Another reason for the polarized effect when no current flows through the reed switch is believed to be that a certain amount of residual magnetic flux is retained in front contact 2 and heel member 4, or both. Because contact 2 and heel member 4 are never driven into saturation, these members are magnetized around a minor hysteresis loop rather than the major hysteresis loop for the material. By operating only on this minor hysteresis loop, residual magnetism in the material never reverses its polarity.

When current flows through the reed switch, an additional stray force is caused to act upon the reed, according to the well-known equation F :BLI

where:

F is the force acting upon the reed,

i3 is the component of magnetic flux density created by the actuating coil and acting perpendicularly upon the reed,

L is the length of the reed, and

I is the amplitude of current flow through the reed.

Depending upon the direction in which the reed switch is offset with respect to the direction of actuating coil flux, for a given direction of coil flux and a given direction of reed current flow, force F acts upon the reed in a direction either aiding or opposing normal pick-up and drop-out forces. This force is believed to be one of the causes for the relay acting in a polarized fashion when current flows through the reed switch.

The present invention relates to a method and apparatus for achieving uniform values of pick-up and dropout current in reed relays, irrespective of polarity applied to the coil. This result is achieved by causing reed switch current to flow in a direction substantially opposite and parallel to the current flowing through the reed switch and in close proximity to the reed switch, so as to substantially cancel the effect of any force acting upon the reed due to interaction of magnetic fields Within the actuating coil and current flow through the reed switch, as well as to oppose the undesired effects of residual magnetism in the reed and front contact.

Because the result of reed switch current flow into and out of the interior of the actuating coil at a single end of the coil is similar to that of adding an auxiliary turn or coil within the actuating coil interior so that its axis is perpendicular to the axis of the actuating coil, it has also been determined that a number of additional turns may be added to the single turn, thereby producing a relay of greatly increased sensitivity without the additional weight, inflexibility and irreversible polarizing effect of a permanent magnet.

One object of this invention is to provide a rugged, compact and fast-acting electromagnetic relay.

Another object is to provide a non-polarized reed relay having uniform pick-up and drop-out values of current independent of current flow direction through the coil or contacts or both.

Another object is to provide a reed relay having an auxiliary winding for increased relay efficiency.

Another object is to provide a reed relay having an auxiliary conductor carrying reed switch current in a direction to create a force at the contacts substantially cancelling any force produced on the reed due to interaction of current flow through the reed switch with an ambient magnetic field.

Another object is to provide a reed relay having an auxiliary conductor carrying current and thereby creating a magnetic field to alter the magnetic field between the reed and contacts due to residual magnetism in the reed and contact materials.

Another object is to provide a reed relay having compensating means permitting highly sensitive operation independent of current flow direction through the actuating coil. 7

-Another object is to provide a reed relay wherein reed switch current provides compensation for non-uniform pick-up and drop-out values of energizing current when energizing current flow is reversed. 7

Another object is to provide a reed relay wherein an auxiliary winding creates a magnetic field perpendicular to that created by the actuating coil in order to alter magnetic attraction between the reed and front contact. Another object is to provide a method and apparatus for selectively biasing a reed relay on pick-up only, dropout only, or both pick-up and drop-out.

Another object is to provide a method of constructing an extremely sensitive non-polarized reed relay.

The invention contemplates a relay comprising a cylindrically-wound actuating coil and a reed switch positioned longitudinally within the coil. The reed switch comprises a rigid, non-magnetic back contact, a rigid, magnetic front contact, and a resilient, magnetic reed abutting the back contact due to reed resilience when the coil is deenergized, and abutting the front contact due to magnetic attraction between the reed and front contact when the coil is energized. A current-carrying conductor is positioned longitudinally within the interior of the coil to create a magnetic field acting through the reed switch in a direction perpendicular to the field produced by the actuating coil. Consistent pick-up and drop-out values of actuating coil current, independent of coil current direction, are thereby achieved.

The foregoing and other objects and advantages of the inventionwill become apparent from the following description when read in conjunction with the accompanying drawings, in which: I

FIG. 1 is a perspective view of one embodiment of the invention, for use where residual magnetism in the reed switch is of low intensity.

FIG. 2 is a front sectional view of a second embodiment of the invention, also for use where residual magnetism in the reed switch is of low intensity.

FIG. 3 is a top sectional view of the second embodiment of the invention taken along line 3-3 of FIG. 2.

FIG. 4 is a top sectional view of a third embodiment of the invention, for use where residual magnetism in the reed switch is of appreciable intensity.

FIGS. 5A, 5B, 5C and 5D are diagrammatic illustrations of magnetic flux paths within the interior of the actuating coil in the embodiment of FIG. 1.

FIGS. 6A, 6B, 6C and 61) are sectional views along line 66 of the diagrammatic illustrations of FIGS. 5A, 5B, 5C and 5D respectively.

FIG. 7 is a diagrammatic illustration of magnetic flux paths within the interior of the actuating coil in the embodiment of FIG. 4.

Referring now to FIG. 1, the relay consists of a hermetically sealed glass enclosure 1, in which are located a pair of contacts 2 and 3. Contact 2 represents a nor mally open, or front contact, while contact 3 represents 4 a normally closed, or back contact. The front and back contacts are cantilever-mounted at one end of enclosure 1, herein referred to as the contact end of the enclosure, by virtue of being sealed therein.

A reed, or heel member 4 is cantilever-mounted at the opposite end of enclosure 1, herein referred to as the reed end of the enclosure, also by virtue of being sealed therein. The reed is positioned between contacts 2 and 3. Flat surfaces of contacts 2 and 3 and reed 4 are located in separate planes parallel to each other. These parallel planes are perpendicular to a fourth plane comprising the plane of travel of reed 4 between contacts 2 and 3. Be-

. cause of inherent resilience of the reed material, when the relay is deenergized, the reed bears against and makes electrical connection with back contact 3 at the contact end of the reed.

Front contact 2 is comprised of a rigid, electrically conductive magnetic material, usually a ferrous alloy. Back contact 3 is comprised of a rigid, electrically conductive non-magnetic material, such a bronze alloy. Reed 4- .is comprised of a resilient, electrically conductive magnetic material, usually a ferrous alloy. The contacts and portion of the reed positioned between the contacts are coated or electroplated with a noble metal such as gold, in order to provide protection against oxidation and corrosion. Further oxidation and corrosion protection is provided by the hermetically sealed enclosure, which may furnish either a vacuum environment for the contact and reed, or alternatively an inert gas environment. The arrangement of apparatus consisting of contacts 2 and 3 and reed 4 positioned within enclosure 1, is generally referred to as a reed switch, indicated by numeral '7 in FIG. 1.

Surrounding the reed switch is a cylindrical actuating coil 5 which provides the magnetic field required to actuate the switch. The coil is wound on a coil form 6 comprised of a suitable electrically non-conductive material, such as nylon. This coil form may be open at either end. A magnetic yoke or shunt 3, preferably comprised of a highly permeable magnetic steel, is mounted in a direction substantially parallel to the axis of coil 5 along the outside of the coil, and is bent around the open ends of the coil, in order to complete a magnetic circuit with reed switch 7. Front contact 2 and reed 4 each penetrate the shunt in .a manner so as to provide respective gaps in the magnetic circuit at the points of penetration. These gaps may be constructed by application of suitable insulation 16 along front contact 2. and reed 4 at their points of penetration through the shunt.

Anon-magnetic electrically conductive strip or wire 9, preferably of copper, is afiixed to reed 4 at a terminal 119 near the end of the reed outside enclosure ll. This end of the reed is herein referred to as the terminal end. Wire 9 longitudinally traverses the interior of coil 5 displaced laterally on one side of the plane of travel of the reed. By carrying reed switch current, wire 9 produces uniform values of pick-up and drop-out current for the relay, regardless of current flow direction through coil 5, in a manner set forth below.

In the unactuated condition of the relay, reed bears against back con-tact 3, making electrical connection therewith. In the actuated condition of the relay, the reed bears against front contact 2, making electrical connection therewith. Because the coatings of noble metal on contact 2 and reed 4 are non-magnetic, a small, nonmagnetic gap exists in the magnetic circuit including reed 4 and front contact 2 at the point where the reed and front contact unite to form an electrical connection when the relay is actuated.

Assume that reed 4 is connected to a source or" direct current through conductor 9, and that separate circuits are connected to front contact 2 and back contact 3. When the relay is actuated, a predetermined value of current in coil 5 is required to pick up the relay by overcoming the resilient force in reed 4 which causes it to bear against contact 3, thereby bringing it to bear against front contact 2. This is accomplished by inducing opposite magnetic poles between front contact 2 and reed 4 due to current flow. through coil 5. Magnetic poles cannot be produced at back contact 3, since the back contact is comprised of non-magnetic material.

Upon decrease of current through coil 5, the relay deenergizes at a value of coil current known as the dropout value. When coil current falls below drop-out value, intensity of the magnetic poles induced in front contact 2 and reed 4 is no longer sufiicient to maintain an attractive force between the front contact and reed great enough to overcome inherent reed resilience tending to force the reed against back contact 3. At this time, reed 4 breaks its electrical connection with front contact 2 and makes electrical connection with back contact 3.

If the direction of current flow through coil 5 should be reversed, pick-up and drop-out values of current are slightly different from the pick-up .and drop-out values determined for the opposite direction of actuating coil current flow. However, if the source of direct current is applied to the reed through the reed end of the coil, in the manner which heretofore has been usual in reed relay practice; that is, without first being passed lengthwise through the interior of the actuating coil along conductor 9, consistent and uniform values of pick-up and drop-out current cannot be achieved. In fact, as reed current amplitude increases, the discrepancy between pick-up values for opposite directions of actuating coil current flow and the discrepancy between drop-out values for opposite directions of actuating coil current flow becomes greater. However, passage of reed switch current through conductor 9 tends to obviate this problem, by producing substantially identical pick-up values and substantially identical drop-out values, regardless of actuating coil current flow direction.

Although the exact reason that presence of conductor 9 produces consistent and uniform values of pick-up and drop-out current seems to be due to a number of factors, it is believed that one of these factors, perhaps the major one, is that magnetic flux produced by current in conductor 9 tends to weaken or strengthen the attractive force between front contact 2 and reed 4 created by the magnetic field of the actuating coil and residual magnetism in the reed and front contact.

Turning now to FIG. 5A for a diagrammatic illustration of flux paths within the actuating coil of the embodiment in FIG. 1, reed 4 and front contact 2 of the reed switch are shown slightly misaligned by an angle With the axis of coil 5. Because of this misalignment, magnetic flux (p created by current flow through coil has a component acting through the reed switch and a component acting perpendicular to the reed switch Component produces magnetic poles at either end of reed 4 and at either end of magnetic front contact 2. Because the poles in the overlapping portions of front contact 2 and reed 4 are of opposite polarity, presence of magnetic field gb causes reed 4 to be attracted to front contact 2 according to the intensity of component Maximum attractive force is created when the reed switch is positioned precisely parallel to fiux path since component is then equal to di Thus, the greater the angle 0 between flux path h and the reed switch, the Weaker the attractive force between reed 4 and contact 2.

When current flows through the reed switch, and angle 6 is of some value other than zero, an additional force is caused to act upon reed 4, as previously pointed out, according to the equation F :BLI

Depending upon whether angle 0 is positive or negative with respect to the direction of coil flux and depending upon the direction of coil flux and direction of reed current flow, force F will act to either aid or oppose normal pick-up and drop-out forces. In FIG. 4A, looking downward upon the reed switch, component is shown acting perpendicular to the reed switch and perpendicu lar to an imaginary plane within which motion of the reed occurs. Component is shown parallel to the reed switch, angle 0 is arbitrarily designated positive, and current is assumed to flow from left to right through the reed switch. The switch may be either in the actuated or unaotuated condition. By application of elementary magnetic flux principles, it can be determined that an additional force F is here produced acting upward from the plane of the drawing, according to the equation F :BLI

where B is the magnetic flux density produced by perpendicular magnetic flux component qb acting on the reed. Another force acting upon the reed is that due to residual magnetism within the reed and within the front contact. This residual magnetism also creates magnetic poles in the reed and front contact which do not change polarity because the field for operating the reed switch is not of sufficient intensity to saturate the material. These poles, in and of themselves, create a magnetic field between the reed and front contact which may either aid or oppose the field induced by magnetic flux component between the reed and front contact. However, the embodiment of FIG. 1 is intended for use where residual magnetism of the reed and front contact are of low intensities and the reed switch is misaligned with the magnetic field within the actuating coil. Under these condi tions, the force created according to the equation F =BLI will have greater effect upon actuation of the reed than residual magnetism in the reed and front contact.

If conductor 9 is connected to terminal 10 under conditions illustrated in FIG. 5A, and a sectional view taken along line 6-6, the result is as diagrammatically illustrated in FIG. 6A. Force F acts upward on reed 4. Current through conductor 9 flows perpendicularly into the plane of the drawing, flux paths 5 are pointed perpendicularly outward from the plane of the drawing, and flux paths are pointed upwards, acting parallel to the direction of motion of reed 4. At section 66 of FIG. 5A, magnetic flux component induces a north pole in front contact 2 and a south pole in reed 4. The effect of the magnetic field produced by current flow through conductor is to create minor magnetic poles in reed 4 and front contact 2, illustrated by ss and ns in FIG. 6A. Thus, under these conditions, the effect of current flow through conductor 9 is to increase the attractive force between the reed and front contact by transversely polarizing the reed and front contact to strengthen the poles induced therein by magnetic flux component e The effect'therefore is to substantially cancel the upward force F acting upon the reed.

FIG. 5B shows the reed switch positioned at the same angle 0 Within the coil, although coil current is now reversed. The direction of coil flux (P is therefore also reversed. In this instance, force F acts downward on reed 4, into the plane of the drawing. Taking a sectional view through line 6-6 in FIG. 5B, the configuration of fields illustrated in FIG. 68 results. Thus, flux component induces a south pole in front contact 2 and a north pole in the reed. The effect of the magnetic field produced by current through conductor 9 is to transversely polarize the reed and front contact and thereby set up minor magnetic poles in reed 4 and front contact 2, illustrated by ss and ns which act in a direction to decrease the attractive force between the reed and front contact. The effect therefore is to substantially cancel the downward force F acting upon the reed.

FIG. 5C shows conditions identical to those of FIG. 5A with the exception that direction of current flow through the reed switch is reversed. Under these conditions a magnetically induced force acts downward upon reed 4, into the plane of the drawing. If a sectional view is taken in FIG. 50 along the line 66, the'configuration of fields illustrated in FIG. 6C results. In this instance, at section d6, magnetic flux induces a south pole in the reed and a north pole in front contact 2. The effect of the magnetic field produced by current through conductor 9 is to set up minor magnetic poles in reed 4 and front contact 2, illustrated by ss and ns. Thus, the effect of current flow through conductor 9 is to decrease the attractive force between the reed and front contact by transversely polarizing the reed and front contact. The effect therefore is to substantially cancel the downward force F acting upon the reed.

FIG. 5D illustrates conditions identical to those illustrated in FIG. 5B, again with the exception that current flow through the reed switch is reversed. Under these conditions, a force F acts on the reed upward from the plane of the drawing. Again, taking a section at line 6-6 in FIG. 5D, magnetic flux qb induces a south pole in front contact 2 and a north pole in the reed. The effect of the magnetic field produced by current through conductor Q is to set up minor magnetic poles in reed 4 and front contact 22, illustrated by ss and ns in FIG. 6D. Thus, the effect of current flow through conductor 9 is to increase the attractive force between the reed and front contact by transversely polarizing the reed and front contact. upward force F acting upon the reed.

Turning now to FIGS. 2 and 3, a second embodiment of the invention is shown wherein a coil of wire 15 is electrically connected to reed 4 at terminal 10. This embodiment is intended for use whereforce F is of appreciable strength. Auxiliary coil 15 is wound in pancake form around enclosure 1, so as to produce a magnetic field perpendicular to the field produced by coil 5. Although a pancake coil is used in this particular configuration, any suitable form of auxiliary coil may be used so long as a flux perpendicular to the flux created by coil 5 is produced; auxiliary coil configuration is dictated only by the requirements of size and space. Theeffect of adding coil 15 is substantially similar to the effect of adding wire 9 to the relay of FIG..1 since it essentially adds a large number of current paths substantially parallel to and in close proximity with the reed switch. Thus, magnetic poles may be induced in front contact 2 and reed 4 in a direction to overcome, any force on the reed produced due to misalignment of the reed switch with the actuating coil axis, regardless of current flow direction in the actuating coil.

FIG. 4 shows how the embodiment of FIGS. 2 and 3 may be adapted to use as a biased reed relay, by providing separate terminals for coil 15, enabling it to be connected toa separate power supply.

Use of auxiliary winding 15 can produce an additional beneficial result by increasing sensitivity of the relay. A reed relay inherently has a high orderof sensitivity, much of it due to low mass of the reed. Sensitivity is further increased by use of magnetic shunt 8, which tends to concentrate magnetic flux produced by coil 5 through the reed 4 and front contact 2 and thereby increase the attractive force between the reed and front contact. Ad-

ditional sensitivity may then be achieved by an increase in ampere turns of winding 15 to create a biasing flux for front contact 2 and reed 4, thereby decreasing both pick-up and drop-out values of current for the relay still further.

Operation of auxiliary coil 15 from an independent power supply also provides means for biasing the relay and overcoming the effect of residual magnetism in the reed and front contact. The biasing effect of the auxiliary coil is reversible and adjustable by controlling current flow therein.

Versatility is further achieved by thefact that the auxiliary coil may be energized from the back contact, rather than the heel, so as to improve pick-up characteristics only. On the other hand, the coil may be energized from The effect therefore is to substantially cancel the I the front contact, so as to improve drop out character istics only.

FIG. 7 illustrates operation of the'reed switch under conditions similar to those illustrated in FIG. 5A, with the exception that force F is not of appreciable value due mainly to the fact that coil flux is now substantially equal to component and component zp is almost zero, creating a low value for B and therefore for F in the equation F :BLI

The reed in this embodiment is substantially in alignment with the longitudinal axis of the actuating coil.

It is obvious that, under these conditions, permissible minor poles induced in the reed and front contact can be of greater intensity than those induced in the configuration of FIG. 5A because of the possibility of greatly increasing the transverse magnetic field of the auxiliary coil passing through the reed and front contact. Moreover, the major factor in altering uniform operation of the reed relay in this embodiment is now residual magnetism in the reed and front contact. This is overcome by the biasing eifect of coil 15. As shown in FIG. 7, the auxiliary coil flux acts in a direction to increase attraction between the reed and the front contact, since residual magnetism in this embodiment acts to decrease the intensity of induced poles in the reed switch. If residual magnetism acts in the reverse direction, current through coil 15 need merely be reversed in direction to decrease the attraction between the reed and front contact.

Although somewhat similar results by way of increased sensitivity may be obtained by use of a permanent magnet in place of the auxiliary winding, a magnet has the major disadvantage of requiring that current flow be in only one direction through the actuating coil and through the reed switch, for proper operation. Thus, although use of a permanent magnet to create a magnetic field perpendicu lar to the field created by the actuating coil may increase relay sensitivity, this increased sensitivity is produced in one direction only. In such case, if current through the actuating coil should be reversed in the presence of a perpendicular field created by a permanent magnet, pick-up and drop-out values of current will increase because the relay now becomes less sensitive than it would be without use of magnet at all. Although this condition also holds true for the instant invention, the invention easily permits the condition to be overcome by simply reversing direction of current flow through the auxiliary coil. A magnet also has obvious further disadvantages such as a relatively large addition of great weight to the relay, loss of flexibility in sensitivity adjustments, and greatly increased shock, vibration and temperature sensitivity.

Shape of coil 15 may be retained by use of a suitable resilient bonding agent, such as silicone rubber, which causes the coil turns to adhere to each other. The auxiliary coil requires no additional support member since it is merely wound around enclosure 1 and supported by reed switch 7. The auxiliary coil is retained in place by inherent resilience of the coil wire which tends to expand the coil against the inside of the coil form. Although tape may also be used to retain the coil configuration, silicone rubber provides the additional advantage of shock protection to the auxiliary winding. Furthermore, it may be used as a filling at either end of the coil form, thereby potting the reed switch auxiliary coil within the actuating coil interior.

Thus, there has been shown a method and apparatus for improving operation of relays of the reed type whereby pick-up and drop-out values of relay current may be decreased in order to improve relay sensitivity, and also may be maintained at uniform values regardless of polarity of energy applied to the relay coil. A highly sensitive, unpolarized, compact relay of minimal power requirements thereby results. Further insensitivity to vibration is attributable to positive positioning of the reed; that is, in

both energized and deenergized conditions, the reed bears against front contact 2 if energized, or back contact 3 if deenergized. Moreover, the relay is characterized by simplicity in construction, resulting in low production costs and ease of manufacture. Finally, sensitivity of the relay is easily adjustable by mere addition or removal of turns on the auxiliary winding.

Although but several embodiments of the present invention have been described, it is to be specifically understood that these forms are selected to facilitate in disclosure of the invention rather than to limit the number of forms which it may assume; various modifications and adaptations may be applied to the specific forms shown to meet requirements of practice without in any manner departing from the spirit or scope of the invention.

What we claim is:

1. An electromagnetic relay comprising a cylindricallywound actuating coil, a reed switch positioned generally coaxially within the coil, the reed switch comprising a reed of magnetic material having one end held stationary with respect to the coil and the other end free to move with respect to the coil, a non-magnetic back contact electrically coupled to the free end of the reed when the coil is deenergized, and a front contact comprised of magnetic material and electrically coupled to the free end of the reed upon energization of the coil, and a conductor positioned longitudinally through the coil and electrically coupled in series with the reed whereby load current carried by the relay flows generally axially through the coil in one direction along the conductor and in the opposite direction through the reed switch.

2. An electromagnetic relay comprising a cylindricallywound actuating coil, 21 reed switch positioned generally coaxially within the coil, the reed switch comprising a reed of resilient magnetic material having one end held stationary with respect to the coil and the other end free to move with respect to the coil, a rigid non-magnetic back contact conductively coupled to the free end of the reed due to inherent reed resilience when the coil is deenergized, and a rigid front contact comprised of magnetic material and conductively coupled to the free end of the reed upon energization of the coil, and a conductor positioned longitudinally through re coil and connected in series with the reed in the vicinity of its stationary end whereby reed switch current flows generally axially through the coil in one di'ection along the conductor and in the opposite direction through the reed switch.

3. An electromagnetic relay comprising a cylindricallywound actuating coil, a reed switch positioned generally coaxially within the coil, the reed switch comprising a reed of magnetic material, a non-magnetic back contact electrically coupled to the reed when the coil is deenergized, and a front contact comprised of magnetic material and electrically coupled to the reed upon energization of the coil, and an auxiliary winding located within the actuating coil and electrically coupled to a source of power, the auxiliary winding being supported by the reed switch to render the axis of the auxiliary winding substantially perpendicular to the axis of the actuating coil whereby actuation of the relay is materially assisted by the magnetic field due to current flowing through the auxiliary winding.

4. An electromagnetic relay comprising a cylindricallywound actuating coil, a reed switch positioned generally coaxially within the coil, the reed switch comprising a reed of resilient magnetic material, a rigid non-magnetic back contact conductively coupled to the reed due to inherent reed resilience when the coil is cleenergized, and a rigid front contact comprised of magnetic material and conductively coupled to the reed upon energization of the coil, and an auxiliary winding positioned within the actuating coil and electrically connected to the reed, the auxiliary winding being supported by the reed switch to render the axis of the auxiliary winding substantially perpendicular to the axis of the actuating coil whereby actuation of the relay is materially assisted by reed switch current flowing through the auxiliary winding.

5. An electromagnetic relay of the reed type comprising a cylindrically-wound actuating coil, a reed switch substantially centrally positioned within the coil in a longitudinal direction, a rigid front contact composed of conductive magnetic material, a rigid back contact composed of conductive non-magnetic material, and a resilient reed composed of conductive magnetic material positioned between the front and back contacts and electrically coupled to the back contact when the relay is deenergized and electrically coupled to the front contact when the relay is energized, the reed being supported from a fixed point relative to the coil at one end of the reed switch and the contacts mounted at the other end of the switch, and conductive means carrying reed switch current coupled to the reed at its terminal end, the conductive means being positioned longitudinally through the coil substantially parallel to the reed switch whereby reed switch cur ent ilows within the interior of the coil in opposite directions, thereby substantially cancelling the effect of a force acting perpendicular to the reed produced by actuating coil magnetic flux when the reed switch is positioned at a slight angle to the longitudinal axis of the actuating coil.

6. An electromagnetic relay of the reed type comprising a cylindrically-wound actuating coil, a reed switch substantially centrally positioned within the coil in a longitudinal direction, a rigid front contact composed of conductive magnetic material, a rigid back contact composed of conductive non-magnetic material, and a resilient reed composed of conductive magnetic material positioned between the front and back contacts and being electrically coupled to the back contact when the relay is deenergized and electrically coupled to the front contact when the relay is energized, the reed being supported from a fixed point relative to the coil at one end of the reed switch and the contacts mounted at the other end of the switch, and conductive means coupled to a source of power and providing a number of current paths substantially parallel to and in close proximity with the reed switch whereby a magnetic field is produced through the reed switch directed substantially perpendicular to the field produced by current in the actuating coil.

7. The electromagnetic relay of claim 6 wherein the conductive means comprises a coil of wire.

8. The electromagnetic relay of claim '7 wherein the conductive means comprises a strip of wire.

it. An electromagnetic relay comprising a cylindrical actuating coil, a reed switch positioned within the coil generally along the longitudinal axis of the coil, the reed switch comprising a front contact and a back contact, each contact being cantilever-mounted near one end of the reed switch, and a resilient electrically conductive reed cantilevenmounted at a fixed point relative to the coil near the other end of the read switch, the reed abutting the back contact when the coil is deenergized and abutting the front contact when the coil is energized, and conductor means coupled to the reed switch at the tenninal end of the reed and longitudinally traversing the cylinder to produce a magnetic field having a component acting through the reed switch perpendicular to the field produced by the actuating coil and of intensity proportional to amplitude of current fiow through the reed.

it An electromagnetic relay comprising a cylindrically-wound actuating coil; a reed switch positioned longitudinally within the coil and comprising a non-magnetic back contact, a magnetic front contact, and a reed of resilient magnetic material abutting the back contact when the coil is deenergized and abutting the front contact when the coil is energized, the front and back contacts being cantilever-mounted within an enclosure close to one end of the reed switch and the reed being cantilevermounted at a fixed point within the enclosure close to the other end of the reed switch; and conducting means positioned longitudinally within the coiland coupled to the reed outside the enclosure whereby current carried in one direction by the reed switch simultaneously flows in the opposite direction substantially axially through the coil interior and substantially parallel to the reed switch, whereby a current equal in amplitude but opposite in direction to current through the reed switch creates a magnetic field which substantially cancels any magnetically induced force on the reed produced due to slight misalignment of the reed with the longitudinal axis of the actuating coil.

11. A sensitive electromagnetic relay comprising an actuating coil producing a magnetic field, a reed switch positioned longitudinally within the actuating coil field, and an auxiliary coil electrically connected to the reed switch and producing a magnetic field perpendicular to the actuating coil field when current flows through the reed switch whereby a magnetic field due to residual flux within the reed switch is substantially cancelled out by the auxiliary coil field.

1.2. An electromagnetic relay comprising a cylindrical actuating coil, a reed switch positioned substantially longitudinally within the coil, the reed switch comprising a non-magnetic back contact, a magnetic front contact, and a reed of resilient magnetic material abutting the back contact when the coil is deenergized and abutting the front contact when the coil is energized, said reed being cantilever-mounted at a fixed point relative to the coil, a magnetic shunt positioned along the outside of the coil and magnetically coupledto the reed and front contact, and a conductor positioned longitudinally through the coil and coupled to the reed in the vicinity of its terminal and whereby load current carried by the relay flows longitudinally through the coil in one direction through the conductor and in the opposite direction through the reed switch.

13. An electromagnetic relay comprising a cylindrical coil, a reed switch positioned longitudinally within the coil and comprising a non-magnetic back contact, a magnetic front contact, and a reed of resilient magnetic material abutting the back contact when the coil is deenergized and abutting the front contact when the coil is energized, a magnetic shunt magnetically coupled to the reed and front contact and positioned along the outside of the coil, and an auxiliary winding located within the actuating coil and electrically connected to the reed, the auxiliary winding being supported by the reed switch to render the axis of the auxiliary winding substantially perpendicular to the axis of the actuating coil whereby operation of the relay is materially assisted by load current flowing through the auxiliary winding.

14. An electromagnetic relay comprising a cylindrical actuating coil, a reed switch positioned within the coil along the longitudinal axis of the coil and comprising a reed consisting of a resilient electrically conductive material cantilever-mounted at a fixed point near a terminal end of the reed switch, and a front and back contact each being cantilever-mounted near the other end of the reed switch, the reed abutting the back contact when the coil is deenergized and abutting the front contact when the coil is energized, a magnetic shunt magnetically coupled to the reed and front contact and electrically insulated from the reed and front contact, the shunt being positioned around the outside of the cylindrical coil, and conductive means connected to the reed switch at the terminal end of the reed, said means being positioned longitudinally through the coil and substantially parallel to the reed switch whereby said means produces a magnetic field through the reed switch having a component perpendicu lar to the field produced by the actuating coil and of intensity proportional to amplitude of current flow through the reed switch.

15. An electromagnetic relay comprising a cylindrically-wound actuating coil; a reed switch positioned longitudinally within the coil and comprising a non-magnetic back contact, a magnetic front contact and a reed of resilient magnetic material abutting the back contact when the coil is deenergized and abutting the front contact when the coil is energized, the front and back contacts being cantilever-mounted within an enclosure close to one end of the reed switch and the reed being cantilever-mounted at a fixed point within the enclosure close to the other end of the reed switch; a magnetic shunt magnetically coupled to the reed and the front contact and electrically insulated from the reed and the front contact, the shunt being positioned along the outside of the actuating coil; and conducting means positioned longitudinally within the coil and connected to the reed outside the enclosure whereby current carried by the reed switch also flows in the opposite direction substantially axially through the coil interior in a direction substantially parallel to the reed switch, whereby current equal in amplitude but opposite in direction to current through the reed switch produces a magnetic field tending to cancel any force on the reed created by the magnetic field produced by current flow through the reed switch.

References @lted by the Examiner UNITED STATES PATENTS 2,481,003 9/49 Curtis 200-87 2,978,556 4/61 Lohs et a1 200-87 2,999,915 9/61 Pfieiderer et a1. 20087 3,125,650 3/64 Ellwood ZOO-87 ROBERT K. SCl-IAEFER, Acting Primary Examiner.

BERNARD A. GILHEANY, Examiner. 

1. AN ELECTROMAGNETIC RELAY COMPRISING A CYLINDRICALLYWOUND ACTUATING COIL, A REED SWITCH POSITIONED GENERALLY COAXIALLY WITHIN THE COIL, THE REED SWITCH COMPRISING A REED OF MAGNETIC MATERIAL HAVING ONE END HELD STATIONARY WITH RESPECT TO THE COIL AND THE OTHER END FREE TO MOVE WITH RESPECT TO THE COIL, A NON-MAGNETIC BACK CONTACT ELECTRICALLY COUPLED TO THE FREE END OF THE REED WHEN THE COIL IS DEENERGIZED, AND A FRONT CONTACT COMPRISED OF MAGNETIC MATERIAL AND ELECTRICALLY COUPLED TO THE FREE END OF THE REED UPON ENERGIZATION OF THE COIL, AND A CONDUCTOR POSITIONED LONGITUDINALLY THROUGH THE COIL AND ELECTRICALLY COUPLED IN SERIES WITH THE REED WHEREBY LOAD CURRENT CARRIED BY THE RELAY FLOWS GENERALLY AXIALLY THROUGH THE COIL IN ONE DIRECTION ALONG THE CONDUCTOR AND IN THE OPPOSITE DIRECTION THROUGH THE REED SWITCH. 